The major conclusion: “A link between the Sun, cosmic rays, aerosols, and liquid-water clouds appears to exist on a global scale…”

This paper confirms 13 years of discoveries that suggest a key role for cosmic rays in climate change. It links observable variations in the world’s cloudiness to laboratory experiments in Copenhagen showing how cosmic rays help generate atmospheric aerosols.

This is important, because it confirms the existence of a sun-earth atmospheric modulation mechanism for clouds and aerosols. It is seen in an event called a Forbush Decrease, which A Forbush decrease is a rapid decrease in the observed galactic cosmic raycoronal mass ejection (CME). It occurs due to the magnetic field of the plasma solar wind sweeping some of the galactic cosmic rays away from Earth. Here is what the Oulu Neutron Monitor plot looked like during such and event on May15th, 2005:

When the CME hit Earth, the magnetic field of the CME deflects the Galactic Cosmic Rays and the secondary particle flux (Neutrons) decreases. In this graph there is also another Forbush decrease visible, which was caused by another, not that powerful flare, which CME passed Earth a few days before this event.

See more from CosmicRays.org Now at last, a linkage has been established on earth showing such events affect cloud cover and aerosols. Luboš Motl gives a good summary ina post from a few days ago, shown below.

Recall that cosmoclimatology of Henrik Svensmark and others postulates that the galactic cosmic rays are able to create “seeds” of low-lying clouds that may cool the Earth’s surface. A higher number of cosmic rays can therefore decrease the temperature. The creation of the cloud nuclei is caused by ionization and resembles the processes in a cloud chamber.

The fluctuations of the cosmic ray flux may occur due to the variable galactic environment as well as the solar activity: a more active Sun protects us from a part of the cosmic rays. It means that a more active Sun decreases the amounts of low-lying clouds, which means that it warms the Earth.

Because the low-lying clouds remove 30 Watts per squared meter in average (over time and the Earth) or so, one has to be very careful not only about the very existence of the clouds but also about the variations of cloudiness by 5% or so which translates to a degree of temperature change.

A systematic effect on the clouds – e.g. one of the cosmic origin – is a nightmare for the champions of the silly CO2 toy model of climatology because the cloud variations easily beat any effect of CO2. Two alarmists, Sloan and Wolfendale, wanted to rule out Svensmark’s theory by looking at the Forbush decreases, specific events of a solar origin named after Scott Forbush who studied them 6 decades ago, involving the plasma. However, their paper was incorrect.

In April 2008, this blog (The Reference Frame) published the following relevant article:

Sloan and Wolfendale complained that no cosmoclimatological signal could have been seen during the Forbush decreases, i.e. short episodes when the activity of our beloved star decreases the amount of cosmic rays reaching Earth. However, Nir Shaviv explained that it should be expected that such a signal is not seen in the averaged monthly data they had used.

In order to see the “tiger in the jungle”, using Svensmark’s words from a press release

that will be published tomorrow (I am allowed to read it now because my uncle lives in Melbourne which already has August), and in order to separate these clean effects from the huge meteorological noise, one needs to increase the temporal resolution to several days and also cover the whole globe to dilute the effects of local weather.

Newest paper

Tomorrow, on August 1st, 2009, Geophysical Research Letters will publish a new paper by Henrik Svensmark, Torsten Bondo, and Jacob Svensmark:

When you click the second link above and obtain an error message, press alt/d and enter to reload the URL: without a direct external link, the PDF file will be displayed correctly. Or open the Google cache as PDF-like HTML.

Svensmark and his collaborators have looked at 26 Forbush events since 1987 (those that were strong according to their impact on the spectrum seen in the low troposphere where it matters): most of them occur close to the solar maxima (in the middle of the 11-year cycles). The observations with a much better temporal resolution imply that the mass of water stored in clouds decreases by 4-7%, with the minimum reached after a nearly 1-week delay needed for the cloud nuclei to get mature. Roughly three billions of tons of water droplets suddenly disappear from the atmosphere (they remain there as vapor, which is more likely to warm the air than to cool it down).

An independent set of measurements has also shown that the amount of aerosols, i.e. potential nuclei of the new clouds, also decreases. All these “strength vs decrease” graphs display a lot of noise but the negative slopes are almost always significant at the 95% level (with one dataset being an exception, at 92%, which is still higher than the official IPCC confidence level that climate change is mostly man-made).

Each Forbush decrease can therefore warm up the Earth by the same temperature change as the effect of all carbon dioxide emitted by the mankind since the beginning of the Industrial Revolution. While you might think that such an effect is temporary and lasts a few weeks only, it is important to notice that similar variations in the solar activity, the solar magnetic field, and the galactic cosmic rays take place at many different conceivable frequencies, so there are almost certainly many effects whose impact on the temperature – through the clouds – is at least equal to the whole effect of man-made carbon dioxide.